Movable support means for center



Nov. 22, 1960 J. A. KUECKEN ETAL 2,951,623

MOVABLE SUPPORT MEANS FOR CENTER CONDUCTOR 0F SLAB LINE Filed March 2'7, 1956 F ql IN VEN TORS. ALBERT A. FOWLER mew A. Kl/EC/fE/V BY A TTO RNEYS United States Patent MOVABLE SUPPORT MEANS FOR GENTER CONDUCTOR OF SLAB LINE.

John A. .Kuec'ken and Albert K. Fowler, North Syracuse, N.Y., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Mar. 27., 1956, Ser. No. 574,344

11 Claims. (Cl. 333-97) This invention relates to amovable support means for thetcenter conductor of a-slab line and, moreparticularly, to such a support means which is configured to provide negligible mismatching of the slab line.

Slab lines, which are wellknown in thev--art,.consist of two spaced parallel plate conductors, havingawidthwhich is large relative to the distance between them, i.e., at least five times, and a center conductor disposed in the medial plane between the two parallel plate conductors. In order to obviate any deleterious fringe effects, the distance, in a direction parallel to the width-of the parallel plate conductors, from the center conductor to either transverse edge of the parallel plate conductors, should beat least two and a half times'the spacing .between the parallel plate conductors.-

Slab lines of the type described above have extremely 1 broad-band, low-reflection characteristics.

It is often desirablethat the center conductor be made movable either transversely or longitudinally within the medial plane descn'bed'above. For instance, it may be necessary to move the center conductor transversely to switch between one of several input or output couplings which couplings are transversely oriented. in the medial plane, or, where the center conductor is employed, in a telescoping variable-length delay line, it may be necessary to move thecenter conductor longitudinally in the medial plane. In such cases, wherethe center-conductor is made movable relative to the parallelplate conductors, it is necessary to provide a support means forthe'center conductors which will not introduce any mismatching.

It is therefore an object of this invention to provide.

a movable support means for the center conductor of a slab line which provides only negligible mismatching.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

Fig. 1 shows in cross section a slab transmission line and illustrates the distribution of the electricfield therein,

Fig. 2 shows in cross section a slab transmission line which incorporates coupling means made in accordance with the principles of this invention, and

Fig. 3 shows in elevation a portion of the slab transmission line of Fig. 2 in the region of the coupling means.

Referring now to Fig, 1, there is shown in cross section aslab transmission line consisting of two parallel plate outer conductors and 12, respectively, and a center conductor 14. Fig. 1 also illustrates' the electric field pattern obtained in a slab transmission line. This electric field pattern is shown by electric flux lines 16 and equipotential lines 18. It will be noted that a zero electric field intensity is'obtained on a line located exactly halfway between parallel plate outer conductors '10- and 12.

Referring now to Figs. 2 and 3, where elements corresponding to elements shown in Fig. 1 are identified by the same reference numerals, there are shown dielectric ribbon members 20 and 22, which extend respectively! from opposite sides of center conductor 14. Ribbon members 20 and 22. respectivelyhave a thickness which is small relative to the diameter of center conductor 14, and have a width which is substantially larger than the thickness thereof. As shown, dielectric ribbon members 20 and 22 are oriented parallel to the width of parallel plate outer conductors 10 and 12 and are symmetrically disposed aboutthe'line located halfway. between parallel plate outer conductors 10 and'1'2.

That end of each of dielectric ribbon members 20 and 22 which is distal to center conductor 14, is, as shown, in contact with and attached to one of the sides of dielectric support members 24'and 26, respectively. Dielectric support members 24 and 26 are, as shown, in rubbing contact with parallel plate outer conductors 10 and 12.

Although it is usually unnecessary to compensate for the added capacitance due to the presence of dielectric ribbon members 20 and 22, at very high frequencies compensation maybe desirable, although not essential. This compensation may be provided by cutting away fiat sections 28 and 30 in center conductor 14: Flat sections 28 and Silare delineated by dashed lines in Figs. 2 and 3.

Referring now to the operation of the invention, center conductor 14 may be. moved either transversely or longitudinally, respectively, by pushing support members 24 or 26, as the case may be, to the left'or right, respective- 1y, or forward or backward, respectively. Since support members 24 and 26 are free to move only in these directions, and cannot move up or down, .center conductor 14 ismaintained at all times 'in the medial plane between parallel plate conductors 10 and 12.

The advantage of this invention is attributed to the fact that dielectric ribbon members 20 and 22 respectively, are relatively thin and are oriented halfway between parallel plate-outer conductors 10 and 12, where the'electric field pattern has a very low density; Therefore, the presence of these mernbers, at all but the highest frequencies, has a negligible effect on the broad band low reflection characteristics of the slab transmission line, and even at these highest frequencies only a very slight effect. At very high frequencies, where the capacitive etfect of members 20, 22, 24 and 26 is no longer negligible, fiat sections 28 and 30 may be used to provide compensation.

In one test model, employing the ribbon configuration of this invention, where the thickness of the ribbon members was 22% of thecenter conductor diameter, a VSWR of 1.02 was obtained up to 2800 me. without compensating flat sections.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope ofthe appended claims the invention may be practiced otherwise than as specifically-described.

We claim:

1. In combination with a slab transmission line having extremely broad-band low reflection characteristics comprising two parallel plate outer conductors spaced from each other by a first given distance, said parallel plate outer conductors having a length which extends the entire length of said line and having a first given width perpendicular to said length thereof which is large relative to said first given distance, .and a center. conductor of less width than said outer conductors, and an axis oriented parallel to said length of said parallel plate outer conductors, said axis coinciding with the .bisector of said given distance, the cross sectional dimensions of said center conductor being substantially smaller than each of said given distance and said given width; dielectric ribbon members disposed in the low density portion of the. electric flux field along the X axis and having a first given thickness which is small relative to the dimension of said center conductor in a direction from one outer conductor to the other, said dielectric ribbon members being disposed at spaced intervals along said center conductor and extending from opposite sides of said center conductor with said first given thickness oriented parallel to said first given distance, and support means respectively connected to the ends of said ribbon members and extending between and having rubbing contact with the outer conductors at substantial distances away from said center conductor.

2. The combination defined in claim 1, wherein said center conductor has fiat sections cut away therefrom which are symmetrically disposed with respect to said ribbon members, said sections lying in planes parallel to said parallel plate outer conductors, and compensating for the added capacitance due to the presence of the dielectric ribbon members.

3. The combination defined in claim 2, wherein each of said fiat sections has a dimension parallel to the length of the axis of said center conductor which is slightly longer than the width of said ribbon members.

4. A slab transmission line having extremely broadband low reflection characteristics comprising two parallel plate outer conductors spaced from each other but in face to face alignment, a center conductor of lesser width than the outer conductors and extending, in a direction lengthwise of the outer conductors, parallel thereto, and between and spaced equally from both outer conductors, dielectric supports at opposite sides of and spaced well from the center conductor and occupying a low density portion of the electric flux field along the X axis and are out of the high density portion of such field, each having its ends abutting and in rubbing contact with the inner faces of the outer conductors, to enable adjustment of the supports sidewise and lengthwise, dielectric ribbon members extending between and engaging the supports and the center conductor, for locating the center conductor relatively to the outer conductors, with the major faces of the ribbons parallel to the inner faces of the outer conductors, said ribbon members being disposed midway between the outer conductors where the electric field pattern has a very low density, each ribbon member having a thickness which is small relatively to the cross sectional dimension of the center conductor in a direction normal to the inside faces of the outer conductors, and a width substantially greater than its thickness but not coextensive with the length of the center conductor.

5. The line as set forth in claim 4, and said center conductor being decreased in thickness, only in the portion along each ribbon member, in a direction normal to the inner faces of the outer conductors, for approximately equal depths on those opposite surfaces of the center conductor nearest the outer conductors, said decreased thickness extending in directions lengthwise of the center conductor equal distances beyond the sides of the free ends of the ribbon members, whereby such decrease in thickness compensates to some extent for the added capacitance at high frequencies due to the presence of the dielectric ribbon members.

6. The line as set forth in claim 4, and said center conductor being circular in cross section, and the ribbon members extending from opposite sides of said center conductor.

7. A slab transmission line having extremely broadband low reflection characteristics comprising two parallel plate outer conductors in aligned face to face relation but spaced apart, a center conductor of considerably lesser width than said outer conductors and extending in a direction lengthwise of the outer conductors and disposed midway between these outer conductors, and dielectric means between the center conductor and the outer conductors, adjustable in directions sidewise and lengthwise of the center conductor, and located largely outside of the electric field pattern, whereby the dielectric means will have a minimum of influence on the capacitance of the line.

8. The line as set forth in claim 7 wherein said dielectric means extends between, and has rubbing contact with faces of the outer conductors, and locates said center conductor approximately midway between said outer conductors whereby said center conductor may be shifted sidewise and lengthwise to limited extents.

9. The line as set forth in claim 7 wherein said dielectric means includes upright supports approximately aligned on opposite sides of the center conductor and extending between and having rubbing contact with the faces of the outer conductors facing the center conductor, and also dielectric ribbon members extending from opposite sides of said center conductor to said upright posts.

10. The line as set forth in claim 9 wherein said conductor has fiat area depressions in the sides thereof towards said outer conductors, with the faces of such areas parallel to the faces of said ribbon members, longer along the center conductor than the widths of the ribbon members, and having their ends extending equal distances beyond the side edges of the ribbon members to compensate for the added capacitance due to the presence of the dielectric ribbon members.

11. A slab transmission line having support means for a center conductor providing negligible mismatching of the slab line, comprising two parallel plate conductors in aligned, face to face relation but spaced apart, a center conductor of considerably lesser width than said outer conductors extending in a direction lengthwise of the plate conductors and disposed midway between those conductors, dielectric supports disposed at intervals along the conductors in pairs, the supports of each pair being arranged opposite one another at opposite sides of said center conductor but extending between and in abutting, rubbing contact with the inner faces of the plate conductors, said supports being disposed in the low density portion of the electric flux field along the X axis and spaced Well from said center conductor, dielectric ribbon members extending between opposite sides of the center conductor and said supports of each pair, midway of the distance between said plate conductors where the electric field pattern has a very low density, with the faces of the ribbon members parallel to the plate conductors, said ribbon members having thicknesses less than the cross sectional dimension of said center conductor in a direction normal to the inside faces of the plate conductors.

References Cited in the file of this patent UNITED STATES PATENTS Weber et al. Dec. 23, 1952 Grieg et al. June 14, 1955 OTHER REFERENCES 

